<?php
session_start();
function random($len) {
	$srcstr = "1a2s3d4f5g6hj8k9l0qwertyuiopzxcvbnm";
	mt_srand();
	$strs = "";
	for ($i = 0; $i < $len; $i++) {
		$strs .= $srcstr[mt_rand(0, 10)];
	}
	return $strs;
}
$str = random(4); //随机生成的字符串

$width = 50; //验证码图片的宽度

$height = 25; //验证码图片的高度

@ header("Content-Type:image/png");

$im = imagecreate($width, $height);

//背景色
$back = imagecolorallocate($im, 0xFF, 0xFF, 0xFF);
//模糊点颜色
$pix = imagecolorallocate($im, 187, 230, 247);
//字体色
$font = imagecolorallocate($im, 41, 163, 238);
//绘模糊作用的点

mt_srand();
for ($i = 0; $i < 1000; $i++) {
	imagesetpixel($im, mt_rand(0, $width), mt_rand(0, $height), $pix);
}
imagestring($im, 5, 7, 5, $str, $font);

imagerectangle($im, 0, 0, $width -1, $height -1, $font);

imagepng($im);

imagedestroy($im);

$str = md5($str);

//SetCookie("authcode", $str, time() + 3600, "/");

$_SESSION["authcode"] = $str;
?>
